1. Field of the Invention
This invention relates to adhesive silicone rubber compositions which adhere well to organic resins, and more particularly, to silicone rubber compositions which adhere well to organic resins, but not to metals.
2. Prior Art
A number of methods have been proposed for providing a bond between addition curing type silicone rubber and organic resins. It is known, for example, to form a bond by applying a primer to a surface of molded resin, applying an uncured silicone rubber material thereto and curing the silicone rubber to the resin or by curing self-adhesive silicone rubber compositions directly to molded resin. For the self-adhesive silicone rubber compositions, a number of proposals have been made on their adhesive agent.
As another approach, it is known from Japanese Patent Publication (JP-B) No. 34311/1990 to add an organohydrogenpolysiloxane containing at least 30 mol % of hydrogen atoms directly attached to silicon atoms to an organic resin so that the resin is bondable with addition curing type silicone rubber. JP-B 45292/1988 discloses integration by physically fitting silicone rubber within a molded organic resin. In Japanese Patent Application Kokai (JP-A) No. 183843/1988, a compound having an aliphatic unsaturated group and a hydrolyzable group attached to a silicon atom is grafted to an olefin resin and silicone rubber is bonded and integrated with the grafted olefin resin. Furthermore, as we previously proposed, a thermoplastic resin can be bonded and integrated to a silicone rubber composition when a compound having an unsaturated group and a hydrogen atom directly attached to a silicon atom is added to the resin (U.S. Ser. No. 07/965,303, now U.S. Pat. No. 5,366,806 and EP 0540259 A1).
However, several problems arise with these prior art methods for integrating silicone rubber and organic resin into a one-piece article. The primer method is cumbersome in that a molded resin shape must be taken out of the mold before the primer can be applied thereto. The method of applying and curing a self-adhesive silicone rubber composition to molded resin has the serious problem that if the resin and silicone rubber are molded into a one-piece member using a mold, the silicone rubber itself adheres to the mold.
Little problem occurs when silicone rubber is coated and cured on resin preforms. However, for several of many general-purpose resins, for example, ABS, PPO, PPS, polycarbonate, acryl, PE, PP and Teflon, self-adhesive silicone rubber compositions of the addition curing type cannot provide a sufficient bond to allow utilization as one-piece articles.
When organohydrogenpolysiloxane is added to olefin resin, the properties of the resin itself can be altered thereby, preventing the resin from exerting its own properties. The physical engagement method leaves a possibility that the two segments will be disengaged by physical forces. When an olefin resin having grafted thereto a compound having an aliphatic unsaturated group and a hydrolyzable group attached to a silicon atom, a primer is required, when the olefin resin is to be joined to an addition curing type silicone rubber.
To take advantage of the weatherability, heat resistance, cleanliness and rubbery elasticity of silicone rubber, the demand that organic resin and silicone rubber be integrally molded into a one-piece article under curing conditions within a short time is increasing. There is a desire to have a silicone rubber composition capable of forming an effective bond to organic resins.